Author

Document Type

Degree Name

Department

Program Name/Specialization

Integrative Biology

Faculty/School

Faculty of Science

First Advisor

Deborah MacLatchy

Advisor Role

Advise

Second Advisor

Jonathan Wilson

Advisor Role

Advise

Third Advisor

Mike Palmer

Advisor Role

Advise

Abstract

Tathlina Lake, NT is an ecologically and culturally important lake to the Ka’a’gee Tu First Nation and supports a small commercial fishery for walleye (Sander vitreus) and a subsistence fishery for lake whitefish (Coregonus clupeaformis). The community is concerned about existing fluctuations in the fish populations. They are also concerned with environmental pressures, including potential future oil and gas development in the near-by Cameron Hills and climate change, and desires to institute long-range biomonitoring in the lake. Male and female adult walleye and lake whitefish, in pre- and post-spawning conditions, were collected biannually in March and August between 2012 and 2016. General health assessment measures included: liversomatic index (LSI), gonadosomatic index (GSI), condition factor and fecundity. Additionally, gonadal and plasma hormone levels were measured to assess reproductive status and determine if seasonal steroid variations can be detected in both plasma and gonadal tissue. In March, pre-spawning female and male walleye exhibited greater LSI, GSI, fecundity and reproductive hormone levels [17β-estradiol (E2) in females and 11-ketotestosterone (11-KT) in males], and unchanged condition factors relative to post-spawning in August. In August, pre-spawning male and female lake whitefish exhibited lower LSI, greater GSI, fecundity and E2 and 11-KT levels, and unchanged condition factors relative to post-spawning in March. Among years, morphometric endpoints were relatively stable within months and reproductive stage and exhibited less variability than hormone levels. Critical effects sizes (CES), which represent natural variability in endpoints, were calculated in order to indicate current ranges of measured variables; fluctuations below or above CES could indicate the presence of environmental pressures on the system and can now be used by the community as the foundation of their long-term biomonitoring protocols. It is recommended that the community focus its long-term biomonitoring on measuring fish condition factor, LSI and GSI biennially (every-other-year) during both pre- and post-spawning seasons using a CES-based approach and that it expand the number of lakes sampled in the region to better represent natural variability and, therefore, enhance the ability to detect change in the region.